[time-nuts] Leap second to be introduced at midnight UTC December 31 this year

Martin Burnicki martin.burnicki at burnicki.net
Wed Jul 20 15:37:02 EDT 2016

Jay Grizzard wrote:
> On Tue, Jul 19, 2016 at 11:39:29PM +0000, Mark Sims wrote:
>> The GPS satellites are now reporting the pending leapsecond...
>> The Z3801A has it messed up...  it says the leap will occur on 30 Sep
>> 2016 (73 days).  The Z3801A has two different messages that report the
>> leap day...  both are wrong. 		 	   		  
> I think some (modern!) Trimble gear may also has a problem. I have an ICM 
> SMT 360 board that's (slowly) flipping back and forth between showing a UTC
> offset of 17 seconds and an offset of 18 seconds. This is their currently
> shipping timekeeping chip, so it's surprising, but I don't know how else
> to explain the behavior outside of a firmware bug.

The UTC/leapsecond data sent by the satellites contains the UTC offset
before and after the leap second event time. This has been 17/17 until
recently, and is 17/18 now.

The GPS satellites didn't start all at the same time to send the new
data set, so there was a period of time where some sats sent 17/17 while
some others already sent 17/18.

So when the GPS receiver always just *showed* information on the current
UTC data set then this is OK. However, the *time* it has *output* should
not have jumped back and forth by 1 second.


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